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Mayo Test ID RAT11 Oxalate/Creatinine Ratio, Urine


Specimen Required


Only orderable as part of a profile. For more information see ROXUR / Oxalate, Random, Urine.


Useful For

Calculating the oxalate concentration per creatinine

Method Name

Only orderable as part of a profile. For more information see ROXUR / Oxalate, Random, Urine.

 

Calculation

Reporting Name

Oxalate/Creatinine Ratio

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  14 days
  Ambient  72 hours

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Oxalate is an end product of glyoxalate and glycerate metabolism. Humans have no enzyme capable of degrading oxalate so it must be eliminated by the kidney.

 

In tubular fluid, oxalate can combine with calcium to form calcium oxalate stones. In addition, high concentrations of oxalate may be toxic for renal cells.

 

Increased urinary oxalate excretion results from inherited enzyme deficiencies (primary hyperoxaluria), gastrointestinal disorders associated with fat malabsorption (secondary hyperoxaluria), or increased oral intake of oxalate-rich foods or vitamin C.

 

Since increased urinary oxalate excretion promotes calcium oxalate stone formation, various strategies are employed to lower oxalate excretion.

Reference Values

Only orderable as part of a profile. For more information see ROXUR / Oxalate, Random, Urine.

 

No established reference values.

Interpretation

An elevated urine oxalate (>0.46 mmol/day) may suggest disease states such as secondary hyperoxaluria (fat malabsorption), primary hyperoxaluria (alanine glyoxalate transferase enzyme deficiency, glyceric dehydrogenase deficiency), idiopathic hyperoxaluria, or excess dietary oxalate or vitamin C intake.

 

In stone-forming patients high urinary oxalate values, sometimes even in the upper limit of the normal range, are treated to reduce the risk of stone formation.

 

The urinary oxalate creatinine ratio varies widely in young children from <0.35 mmol/mL at birth to <0.15 mmol/mL at 1 year to <0.10 mmol/mL at 10 years and <0.05 mmol/mL at 20 years of age (see table below).(1)

Oxalate/Creatinine (mg/mg)

Age (year)

95th Percentile

0-0.5

<0.175

0.5-1

<0.139

1-2

<0.103

2-3

<0.08

3-5

<0.064

5-7

<0.056

7-17

<0.048

Cautions

Ingestion of ascorbic acid (>2 g/day) may falsely elevate the measured urinary oxalate excretion.

Clinical Reference

1. Matos V, Van Melle G, Werner D, Bardy D, Guignard JP: Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis. 1999;34:e1

2. Wilson DM, Liedtke RR: Modified enzyme-based colorimetric assay of urinary and plasma oxalate with improved sensitivity and no ascorbate interference: reference values and sample handling procedures. Clin Chem. 1991;37:1229-1235

3. Lieske JC, Wang X: Heritable traits that contribute to nephrolithiasis. Urolithiasis. 2019 Feb;47(1):5-10

4. Lieske JC, Turner ST, Edeh SN, Smith JA, Kardia SLR: Heritability of urinary traits that contribute to nephrolithiasis. Clin J Am Soc Nephrol. 2014 May;9(5):943-950. doi: 10.2215/CJN.08210813

5. Zhao F, Bergstralh EJ, Mehta RA, et al: Predictors of incident ESRD among patients with primary hyperoxaluria presenting prior to kidney failure. Clin J Am Soc Nephrol. 2016 Jan 7;11(1):119-126. doi: 10.2215/CJN.02810315

Method Description

This test calculates the oxalate concentration per creatinine. This calculation is performed in Soft.

Day(s) Performed

Monday through Saturday

Report Available

3 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

Not Applicable

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RAT11 Oxalate/Creatinine Ratio 13483-3

 

Result ID Test Result Name Result LOINC Value
RAT11 Oxalate/Creatinine Ratio 13483-3